5-aminolevulinic acid photodynamic therapy enhance the effect of acitretin on squamous cell carcinoma cells: An in vitro study

Squamous cell carcinoma (SCC) remains the second most common nonmelanoma skin cancer (NMSC) worldwide. Both acitretin and 5-Aminolevulinic acid mediated photodynamic therapy (ALA-PDT) have validated effect on SCC. However, the effects of both treatmens remain limited, and there has been no report concerning the potential synergistic effect of both treatments for SCC. Objective: To investigate the cytotoxic effect of acitretin on SCL-1 cells, and whether ALA-PDT enhances this effect. Methods: CCK-8 and trypan blue exclusion array were used to detect the cell cytotoxicity after acitretin treatment with different concentrations (1.6 x 10(-4)mg/mL, 1.6 x 10(-3)mg/mL, 1.6 x 10(-2)mg/mL and 1.6 x 10(-1)mg/mL) for 24 h, 48 h and 72 h. Flow cytometry and trypan blue exclusion assay were used to detect the apoptosis and viability of SCL-1 cells after treated with acitretin, ALA-PDT and ALA-PDT immediately followed by acitretin. Independent sample t test was used to analyze the different incubation time of acitretin and acitretin combined with ALA-PDT on SCL-1 cells. Bonferroni Test One-way Anova method was used to analyze the effect of different treatment on the SCL-1 cells. Results: A significant cytotoxic effect was observed after acitretin treatment, in an acitretin concentration-dependent manner within the range of 1.6 x 10(-4)mg/mL to 1.6 x 10(-1)mg/mL and an acitretin incubation timedependent manner within 24 h-72 h. The total apoptosis rate and dead cells rate in group of ALA-PDT combined with acitretin were both significantly higher than that of acitretin, ALA-PDT group. A stronger apoptotic and cytotoxic effect detected 24 h after treated with acitretin than that of 12 h was observed in this study. Conclusion: Acitretin has a cytotoxic effect on SCL-1 cells, and ALA-PDT treatment enhances the the cytotoxic effect of acitretin.